1. Field of the Invention
The present invention relates to a mobile communication system. More particularly, the present invention relates to an apparatus and a method for configuring and managing/controlling a cluster, which is a set of Base Stations (BSs) for transmitting signals cooperatively.
2. Description of the Related Art
A cellular system, such as a mobile communication system, is a system proposed to overcome a limitation of a service area and a limitation of subscriber accommodation capacity. In this cellular system, several methods of increasing capacity of the system, such as a method of increasing the number of channels per unit size, and the like, have been actively studied.
Recently, in a communication network, such as a Virtual Cellular Network (VCN), several methods of increasing capacity of a system have been also considered. The VCN provides environments in which BSs reuse their space with one another and share data with one another. For example, small BSs capable of being easily installed/changed/deleted are placed in a VCN based on wireless backhaul. Because of sharing data among the BSs, if interference between clusters which are a set of the limited number of data sharing small BSs may be addressed, it is possible to increase capacity of a system. However, because the number of cooperative BSs considering a backhaul/complexity/channel estimation overhead is limited in VCN environments, an interference problem between clusters has been generated.
A disjoint clustering method and an overlapped clustering method have been proposed as methods of addressing interference between clusters. In accordance with the disjoint clustering method, clustering between BS clusters is performed to apply network Multi-Input Multi-Output (MIMO). Herein, each of the clusters is equipped with disjoint BS subsets. However, although the disjoint clustering method is performed, because there still is the interference problem between clusters, the fact that a solution for an interference problem between clusters of low complexity is requested is disclosed by L. Wang, C. J. Yeh who published “3-cell network MIMO architectures with sectorization and fractional frequency reuse” on June 2011 in the Institute of Electrical and Electronics Engineers (IEEE) Journal in Selected Areas of Communications (JSAC).
In accordance with the overlapped clustering method, it is permitted that each BS may belong to two or more clusters and a generation frequency of an interference problem between users who are located on a boundary between clusters is minimized. In one example, a multi-cell network MIMO scheduling method was proposed by S. Kaviani and W. A. Krzymien who published “Multicell scheduling in network MIMO” in Globecom 2010. However, in this method, complexity for a beamforming configuration is increased in comparison with performance improvement. In addition, the method is not linked to resource allocation, such as frequency reuse. In another example, a “intertwined clustering” method for forming different cluster patterns while being classified according to time/frequency resources was proposed, according to the invention, which is filed on May 24, 2010 to have a patent application Ser. No. 12/786,285, is published on Dec. 2, 2010 to have a patent publication number 2010/0304773, and is entitled “A method for selective antenna activation and per antenna or per antenna group power assignments in cooperative signaling wireless MIMO systems”, by inventor Sean A. Ramprashad. However, this method has a limitation of a concept level or a limitation that only an operation in fixed BS distribution environments based on hexagonal cells is considered.
Therefore, a need exists for an apparatus and a method for configuring and managing/controlling a cluster which is a set of BSs for transmitting signals cooperatively.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present invention.